Package, preferably for dry and frozen material, and an arrangement for the production of such a package

ABSTRACT

A package of polygonal cross section having a thin end closure closing at least one end. The closure extends over onto and is attached to the sides of the package. Airtightness is improved by attaching the closure such that the end of the package is bent inwardly at least at the corner, in somewhat the form of a frustrum pyramid. An apparatus for closing such a package comprises a heatable tool having inwardly sloping sides to press the end closure onto the edge of the package end and concurrently force the end into the frustrum pyramid shape.

I United States Patent [151 3,647,133 Christensson 1 Mar. 7, 1972 [54]PACKAGE, PREFERABLY FOR DRY 2,690,288 9/1954 Allen et a1 ..229/5.5 X

AND FROZEN MATERIAL, AND AN 2, 2,093 2/1959 Chap ARRANGEMENT FOR THEPRODUCTION OF SUCH A PACKAGE 3:050:229 8/1962 Neff ..229/51 TS X 72 l t:OdWikm-Chiste B 1 Stockholm, FOREIGN PATENTS 0R APPLICATIONS 284 64811/1952 Switzerland ..229/37 E 3 l gm o [7 Ass'gnee gebohg, fifg f j fgfggg fi 902,601 8/1962 Great Britain ..229/55 Sweden 7 PrimaryExaminer-Davis T. Moorhead [22] Filed: Aug. 20, 1970 Attorney-Larson,Taylor and Hinds [21] Appl. No.: 65,491 [57] ABSTRACT 52] U S Cl 229/37229/3 5 229/51 Ts A package of polygonal cross section having a thin endclosure [51] B65d 6 365d 5/54 closing at least one end. The closureextends over onto and is [58] Fieid R 5 5 3 l l 5 R attached to thesides of the package. Airtightness is improved by attaching the closuresuch that the end of the package is bent inwardly at least at the comer,in somewhat the form of a [56] Reierences Cited frustrum pyramid. Anapparatus for closing such a package comprises a heatable tool havinginwardly sloping sides to UNITED STATES PATENTS press the end closureonto the edge of the package end and 2 41 l 622 1 H1946 G l I 229/3 5concurrently force the end into the frustrum pyramid shape.

uyer et a 2,562,579 7/1951 Ringler ..229/37 E X 5 Claims, 6 DrawingFigures l8 I 7 IO PATENTEBMAR 1 m2 INVENIOI 00 W. CHRI STENSSON 9451604Ja /w gar/s ATTORNEYS PACKAGE, PREFERABLY FOR DRY AND FROZEN MATERIAL,AND AN ARRANGEMENT FOR THE PRODUCTION OF SUCH A PACKAGE FIELD OF THEINVENTION This invention relates to packages, preferably for dry andfrozen materials, and particularly to closures and manner of applyingsuch closures.

BACKGROUND AND SUMMARY OF THE INVENTION Within the packaging industry,attention to a continuously increasing rate has been directed toward thetask of achieving economical manufacture, and especially towardachieving economies in consumption of materials. One of the mostopportune areas in which such economies may be achieved is in the designof the package blanks such that there will be a minimum wastage ofmaterial when the blanks are stamped out from a given piece ofmaterial,v such as cardboard. wastage of material commonly occurs in thecorner surfaces and the like between the side surfaces of a package andits adjacent parts forming the closing flaps. The more closely a packageblank approaches a completely rectangular outer contour, the less willbe the wastage of material, and the greater will be the number ofpackage blanks which may be stamped from a given piece of cardboard orthe like.

Packages, however, must be reasonably tight. In many cases, such aswhere a vacuum exists inside of the package, complete tightness isrequired, and it is difficult to achieve this complete tightness whilealso effecting a reduction in the amount of material used. In othercases, although such complete tightness may not be required, itnevertheless is important to obtain the best possible tightness underthe circumstances. This is especially so in those packaging instanceswhere it is important to prevent passage of moisture from or to theinterior of the package. For instance, when dried products are packed,it is important to prevent moisture entering the package from theoutside air, and when frozen products are packaged, it is important toprevent leakage of moisture or liquid from the package. Such driedproducts might include cakes, roasted nuts, chips, etc. An example of afrozen product would include ice cream, for instance. An example of deepfrozen products would include many different kinds of cooked vegetables,which may be frozen liquid in order to retain their moistureconsistency.

Exemplary of packages which have been developed in an ef fort to achieveeconomies of material while at the same time achieving satisfactorytightness is a package of polygonal, preferably rectangular crosssection, which is produced'by folding a piece of cardboard along givencreasing lines, whereby pasting flips are arranged at the upper andperhaps also at the lower end of the package, an end closing piece of athinner, easily bendable material being attached to the pasting flaps.In a package of this type, it is especially important to ensuretightness at the sides and the corners, where the cardboard of the sidesmeets the end closing piece. For achieving improved tightness in theseareas, various solutions have been proposed. Included among these is aprocedure wherein the closing flaps on the main part of the package,which is made of cardboard, are cut in inclined directions at theirends, sothat the slanting edges will contact each other when thecardboard blank has been folded into its form, polygonal in crosssection. The cardboard piece may be made from cardboard covered byplastic on at least one side, but preferably on both sides, and theplastic by which the cardboard piece is covered may be heat weldable.Thereby the end closing parts may also comprise a thin foil of heatclosable or weldable plastic. However, even in packages constructed inthis manner, it has been found that the required tightness often is notachieved. Investigations have shown that this shortcoming apparentlystems from the extremely small, but nevertheless relatively substantial,openings occurring at the corners of the package. The slot between theslanting flaps apparently acts as an air passage, directly into or fromthe comer, and the mouth of this air passage situated in the corner isnotcovcred satisfactorily by the plastic foil lying over the package. Ithas, therefore, further been proposed to make the plastic foil biggerthan the end surface of the package part made of cardboard, whereby anendpiece of the plastic foil will be available to be folded down ontothe package sides. In this way, one would expect that a substantiallybetter tightness would be achieved, but surprisingly enough, thetightness still is often unsatisfactory. Further investigations in thisarea form the basis of the instant invention.

To weld the plastic foil over the mouth of the package, it is necessarythat the foil will be heated, at least in those areas which are to bewelded. Upon heating, the plastic foil is weakened and made formable,but simultaneously it is subjected to temperature extension or expansionmovement, which will not correspond to any similar extension of thecentral parts of the foil piece, and this will cause folding of the edgepart of the plastic foil, folded around the upper and the lower edge ofthe package. When welded, this edge part will attach to the upper edgeof the cardboard close to its mouth by such a strong bond that nosliding in the bond will be possible upon the subsequent cooling of theplastic foil. The consequence will be that folds will be created in theplastic foil, which on the one hand are so small that they generallycannot be observed by the naked eye, but'which, on the other hand,together represent a sufficient path between the interior of the packageand the exterior air that communication will be created to a disturbingdegree.

As a result of the investigation, and the detection of the apparentreason for the lack of tightness, a basic remedying feature of thepresent invention was developed, namely, during the welding when theplastic is still in a weak and forrnable state, to force the utmost edgepart of the cardboard as well as the plastic foil inwardly under such apressure that the folding tendency of the plastic foil will cause aflattening, by which the channels,which would otherwise be created, areavoided.

The present invention thus is directed to a package of polygonal,preferably rectangular, cross section, which is produced by folding apiece of cardboard along given creasing lines, whereby inwardly directedpasting flaps are-provided at the=upper and perhaps also at the lowerend of the package, to which an end closing piece of a thinner, easilybendable material is attached. The pasting flaps on the main part of thepackage, which is made of cardboard, are cut in an inclined direction attheir ends, so that the sloping ends will at least approximately contacteach other when the cardboard blank is folded into its form, polygonalin cross section. The end closing part comprises a thin foil of aheat-scalable material, preferably of plastic, which may be welded tothe preferably also plastic-covered cardboard of the package, and theend closing piece extends beyond the edge of the cardboard part of thepackage by a free edge part, which is intended to be folded down ontothe cardboard sides and to be attached to them.

According to the invention, the free edge of the end closing piece alongwith the part of the cardboard piece of the package correspondingthereto, which was initially composed of four even sides, has, at leastat the corners of the package but preferably all around the package,after the forming of the package, in connection with the'welding of theend closure to the cardboard, been formed as a short frustum of apyramid with its sides sloping inwardly in the direction toward the endof the package, so that a flattening has taken place of the edges of theend closure, which were extended due to the heating to weldingtemperature, and consequently the tightness has been improved. Theinvention also relates to an arrangement for the production of such apackage.

According to the invention, as it relates to such an arrangement, thearrangement contains a welding tool provided with inwardly turned slopedsides of such a form that they will simultaneously by pressure fromtheir sloping sides provide the deformation of the upper part of thepackage duringreformation of this part to its frustum pyramidal form andadd heat for providing the fixture of the free edge of the end closureto the side of the package by welding.

The invention will be further described below in connection with apreferred embodiment thereof illustrated in the attached drawings, butit is to be understood that the invention is not limited to thisspecific embodiment or form of execution, but that differentmodifications may occur within the framework of the invention.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows the cardboard blank of thepackage after it has been stamped out and creased.

FIG. 2 illustrates in perspective a finished package according to thepreviously proposed method for its closing.

FIG. 3 is a plan view of the end closing part.

FIG. 4 shows in increased scale a section through the edge part of thepackage which has been surrounded in FIG. 2 by a circle.

FIG. 5 shows the corresponding corner or edge part, modified accordingto the present invention.

FIG. 6 shows a tool for effecting the closure of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT The package blank according toFIG. 1 contains two short sides 10 and 11 and two long sides 12 and 13,separated by means of creasing lines 14, 15 and 16. Further there is aclosing flap, comprising two parts 17 and 18 mutually separated by meansof a creasing line 19 and connected to the long side 13 by means of asecond creasing line 20. The part 18 is intended to form the closingflap proper, which should be attached to the edge of the short side 10when the package has been folded into its form rectangular in crosssection, whereas the part 17 is intended as a grip tongue for openingthe package. For making the opening of the package easier, a perforationdevice is also made. This may be of any kind known per se, and it maycomprises cuts, arranged in pairs, which however do not run completelythrough the thickness of the cardboard. In each couple of such lines theone is cut in from the front side of the cardboard and the other onefrom the back side. For illustrating this, the line out from the outerside of the cardboard has been indicated in the drawing by means of aline, composed alternatively by one dash and one dot, whereas the linecut into the inner side of the cardboard has been indicated byalternatively one dash and two dots. The

two lines 21 and 22 or 23 and 24 consequently will give a tearing deviceeasy to open, at the opening of which the cardboard will be slottedbetween the two lines, contained in one single pair ofsuch lines.

At each end of the four sides 10, ll, 12 and 13 of the package, furtherpasting flaps 25-28 and 29-32, respectively are arranged. These flapsare cut in sloping direction in their ends, so that when the package isfolded into its form rectangular in cross section, the edges willcontact each other at 45 angles, as seen from FIG. 2.

In order that the part 17 shall serve as a grip tongue for an easyopening of the package, it should be free from the package in otherparts than along the creasing line 19, and for this reason, at thestamping of the package blank cuts 33 and 34 are arranged at the ends ofthe inner part of the grip tongue 17. The short pieces of the part 17outside of these cuts therefore are attached to the surface of theclosing flap 18 without perforation or creasing.

When folded the package blank according to FIG. 1 into a package, thefour sides 10, 11, 12 and 13 are bent perpendicularily to each other,and the flaps 25-28 and 29-32 are folded inwardly at least approximatelyat right angles to the levels of the sides concerned. The inner side ofthe flap 18 and/or the outer side of the edge of the side 10 is providedwith paste, glue or some other means for joining together the package,and one then has a package, shaped as shown in FIG. 2, after the flaps25-32 have been provided in the way indicated below with their endclosing parts. One will see that the tearing tongue is inclined at asmall angle, so that this tongue is easily available for opening thepackage.

In practice it will occur as a rule that the package has been producedby a given manufacturer of packages, delivering the package in evenlycollapsed state to the enterprise, which will pack its products therein.Thereby it is quite natural, that the package is folded around full 180along the creasing lines 14 and 16, whereas, on the other hand, thecreasing lines 15 and 20 are left unfolded, whereafter the gluing bymeans of the tongue flange 18 takes place. The user of the packagethereafter has to break it up into its form, rectangular in crosssection, before closing it in the below indicated way.

It is especially suitable to make the package blank from a cardboard,covered on both sides by a thermoplastic. The attachment along the flap18 then takes place by plastic welding under addition of heat.

An end closure is shown in FIG. 3. This end closure is made from arather thin and easily bendable and formable material, preferably also aplastic, which is heat weldable. It is applied over the still open mouthof the package according to FIG. 2, so that the dotted lines 35 willcorrespond to the creasing edges between the sides 10-13 of the packageand the flaps 25-28 or 29-32, respectively, connected to them. One hascut the plastic piece somewhat bigger than the upper side of thepackage, so that it will have an edge all around to be folded downagainst the sides of the package. In this way one could by a minimum ofstamping waste material provide a package, which one believed whencarefully closed to be hermetically tight. To the question of thistightness we will return below.

FIG. 4 shows in enlarged scale the piece of FIG. 2, which has beensurrounded by the circle 37. The creasing line 38, as one will see, isfolded about a angle, so that the side 13 and the flap 28 will be normalto each other connected by a slight rounding, and the end closure willbe attached to the flap 28 and the folded down edge part 36 to the side13.

The tightness, which was expected to be created in a package accordingto the above, however, did not happen to occur. The investigationsforming basis of the present invention have produced at least oneexplanation thereof. When welding the end closure 135 made of plastic tothe package, it must be heated in the welded part to weldingtemperature. For practical reasons one cannot heat all of the piece 135to this temperature, because it would in such a case be so weak, that itcould thereafter no longer be kept in an even position over the mouth ofthe package. A great difference in temperature will therefore existduring the welding procedure, between the interior parts of the endclosure 135, on the one hand, and the edge part 36 of same piece, on theother hand. This difference in temperature causes heat elongation of theedge parts, by which they are folded in wave form. The plastic is soweak and plastic, that after the welding is completed, and cooling isadded, these waves will not again be equalized, but they will remain,and openings will therefore be created between the folded-down edgeparts 36 of the plastic and the cardboard inside of this edge. At least,it is through these openings that the communication will later on becreated between the interior of the package and the space outside of thepackage, so that said package will be untight.

The invention provides that one should press the extending edge parts 36of the end closure inwardly onto the corresponding uppermost orlowermost edge part of the package side all around the package by meansof a tool with a sloping pressure surface, so that the surplus ofplastic in the edge parts 36 is pressed evenly under influence of aninwardly acting, wedge-formed applied pressure from a tool, and anoutwardly acting pressure in the form of the resistance of the cardboardmaterial against deformation, so that after completed welding of theparts of the end closure placed outside of the upper side of thecardboard, this specific edge part of the package will be inclinedinwardly in the form of a thin frustum pyramid. The section through thispyramid is shown in FIG. 5 in a scale, corresponding to the one used inFIG. 4. The reference numerals are the same ones as used in FIG. 4. Onewill especially observe, that by the pressure of the uppermost edge partof the package sides no deformation needs to be created regarding theflaps 25-28, because all of this deformation may be received in thecreasing line 38.

The arrangement used for causing the fixture of the end closure, ofcourse, will either be the same or different at the lower end and at theupper end of the package. This depends the fact that the package isusually empty when it is closed at its lower end, but it is filled, whenclosed at its upper end. Consequently, one may if desired put a mandrelinto the package when closing the lower end, but one would use suctionnozzles at the closure of the upper end of the package. The closing ofthe end of the package under insertion of a mandrel is extremely wellknown, and therefore no specific description thereof would be required,but it is probable that it has not earlier happened that one usedsuction nozzles for keeping out the upper piece against being suckeddown into the package, and therefore the arrangement according to FIG. 6has been shown using this procedure.

The package 9 has been shown in FIG. 6, kept in place between a coupleof arms 40 and 41. Of course, it may also be supported on a table, whichhas not been shown in the drawing. The end closure 135 extends in a wayalready described outside of the upper edge of the package 9. This endclosure is kept in place by means of a suction nozzle device 42 with ahead 43, carried by a hollow shaft 44, so that it can be displaced alongwith the head 43 within a cavity 45 in the welding head 46. The weldinghead 46 in its turn is carried by a head 47, in which a second controlshaft 48 meshes. Further, the welding head 46 carries by means of athermally insulating piece 49 a coupling box 50, in which by means ofthe fixture 51 an electrical cable 52 is carried for feeding electricalcurrent. The cable 52 runs to a connection plinth .53, from whichconductors 54 run to one or a plurality of heater elements 55 in theinterior of the welding head 46.

The arrangement now described functions in the following way: By meansof the arms 40, 41 the arrangement has caught a package 9, which is, oris to be, provided with an end closure 135, and has brought it into theposition, in which his shown in FIG. 6. The welding head 46 has made aswinging movement about its shaft 48, so that it has moved completelyoutside of the range of the caught package 9. The conduit in theinterior of the shaft 44 is thereafter put under vacuum, after thewelding head has been brought into position above a column of ready cutend closures 135, so that the end closure is kept in correct position bythe vacuum conduits 56. Thereafter the welding head 46 is again swungover the package 9 and is lowered down onto this package into a positionas shown in FIG. 6.

Already earlier electrical current has been fed through the cable 52,the distribution plinth 53 and the cables 54 to the heater elements 55,so that the welding head 46 has assumed the temperature required for thewelding. By means of the shaft 48 the welding head 46 is lowered downover the package 9 along with the end closure I35. Thereby the weldinghead 46 will by means of the wedge-formed, sloped surface 57 first pressdown the surplus part 36 of the end closure 135 against the sides of thepackage 9 and thereafter press the upper edge part of these sides alongwith the free edge 36 of the end closure 135, so that a deformation willtake place simultaneously with a compression of all of the folds whichcould have been created in the edge part 36 of the end closure 135, andthe package will in its upper part take the form which is shown inenlarged scale in FIG. 5.

It cannot be avoided that a given heat quantity is also transferred fromthe welding head 46 to the part of the end closure 135 which shouldremain even. The outermost parts of this even part of the end closure135 therefore will also fold themselves under extension of surface, andit may then be important in some regular way to assume this foldingaction in order, when cooling the end closure again, to make thereceived part free. Amongst others, it is for this reason that thewelding head has been provided inside of the sloped surface 57 with ateethformed border 58, running all around and so arranged that it willmesh inside of the edge of the package 9 and there weakly press theoutermost part of the end closure 135 down for receiving its surfaceincreased by heat development. This arrangement, however, has also afurther purpose, .which may be regarded at least as important, viz, tomake sure that the welding bond between the edge 36 of the end closureI35 and the edge of the package 9 will extend around the upper edge andthereby exist against the edge part of the outer side of the package aswell against the narrow closing flaps, which may accidentally by thepressure from the tooth 58 be bent somewhat downwardly, but afterlifting up the welding head will again by the resilient force in thecreasing lines assume their position perpendicular to the packagesides.

When executing the invention as hitherto described, it has been found,however, that even now complete tightness could not be obtained in alltreated packages. Certainly, the plurality of them have been tight to asatisfactory degree, but singular samples have, without the treatmenthaving been in the slightest way different, proved to be untight. Aftersubstantial difficulty, it was found that this sporadically occurringuntightness depended upon a specific occurrence in the corners of thepackage in connection with the used welding temperature.

In the corners of the upper edge of the package the sides are bent bythe welding head in 90 angle. At the sides, they extend however instraight line on each side of each welding point. The consequencethereof will be, that heat is fed to the singular welding point over anangle of only 90 at the corners, but on the other hand over an angle ofl at the sides. The heat feeding at the corners will therefore be lessper unit of weight of the plastic material in the end closure I35.Simultaneously this end closure is bent down around the corner, so thata twofold folding will be created, viz firstly the folding, which alsooccurs at the sides, and which depends upon the heat enlargement of thematerial, and secondly also the folding required for receiving thesurplus of material at the corners. The consequence will be, that onewill simultaneously get a decreased feed of heat at the corners and agreater quantity of plastic receiving the heat which is fed, and thattherefore the temperature of the plastic in the comer will be rathermuch lower than in the plastic along the sides. This in turn causes arisk of cold welding with consequent -untightcuess.

Assuming that this explanation of the existing untightness wassufficient and reliable, it was thereafter obvious, that one had inorder to get the same welding relations for the plastic in the cornersof the end closure and along its sides firstly to increase thetemperature at the corners of the welding head, secondly also todecrease the quantity of plastic contained in the corner formations ofthe end closure. The first one is practically not possible to provide,because the welding head must be made from a good heat conductingmaterial, and by the good heat conduction and equalization oftemperature will take place. On the other side it is possible todecrease the quantity of plastic in the corner formations by cuttingthem off in a way, shown in FIG. 3 at 59.

Immediately, it proved that this visually unessential step caused therisk of leakage at the comers to be practically completely eliminated.By the cutting off, as a matter of fact, the heat consuming quantity ofplastic was so strongly decreased, that the temperature exactly andsurely would be above the limit temperature for cold welding, whereas itearlier balanced about this limit temperature and in some cases it wasfor reasons, which one could not find out,.below this limit temperature,in other cases however above the limit temperature.

When deciding how far the corner cutting of the upper piece should takeplace one was guided by the following pints of view: the stronger thecorner cutting is, the less will the surplus of material be, which byassuming part of the welding heat causes a decrease of the weldingtemperature. Simultaneously, however, the distance from the corner 60 ofthe package to the cutting line 59 will be smaller, and this means thatthe surplus strip of plastic of the end closure in the corner will beless, with a risk that it will-be too narrow and cause a leakage inanother way than the above mentioned one. In tests it proved that onewill get a good compromise between these two points of viewcounteracting each other by cutting the comer of the end closure so thatthe distance between the proper corner 60 of the package and the cuttingline 59 will be about equal to two thirds of the width of the surpluspiece of the end closure along its straight sides.

in practical tests it has now proved that the leakage caused due tofolding of the edge part 36 of the end closure 135 will be mostdifficult at the corners, and therefore one has also investigated theaction of only pressing in the package along with the edge part of theend closure at the corners. Curiously enough, it was found thereby thatthe risk for leakage along the sides of the package was essentiallysmaller. It is not quite clear, what the reason to this may be, but onemay assume that the folding at the sides at least in part has beencaused by displacement tensions in the proper level of the plasticpiece. By attaching the plastic piece in a more rigid way at the cornerthese displacement tensions are decreased, and one may in many a caseachieve a completely satisfactory result without the middle parts of theupper edges of the package sides being subjected to the sloped pressing.The invention therefore also shall comprise such a partial use of theinventional idea.

I claim:

1. A package having a base portion of a polygonal cross section which isproduced by folding a blank of stiff material such as cardboard or thelike along creased lines such that at least one end of the packagecomprises inwardly directed pasting flaps, a thin foil end closureattached at said end, said pasting flaps being cut at their ends suchthat the ends of the flaps approximately contact each other when thecardboard blank is folded to its form, polygonal in cross section, thesaid end closure of the package at said end comprising a heat-scalablematerial capable of being heat sealed against the cardboard at the saidend of the package and the end closure part including a free edgeextending outside of the edge of the base portion of the package andadapted to be folded down against the outside of the sides of the baseportion and to be attached to the sides thereof, the free edge of thesaid end closure, together with the part of the base portion connectedthereto, at least adjacent to the corners between adjacent sides of thebase portion and at said end, being bent inwardly towards the center ofthe package such that the bent end portions at said end form a frustrumpyramid with'the sides at least at said corners, sloping inwardly in thedirection toward the end of the package such that a flattening takesplace of the said free edges of the end closure against the base portionto provide an airtight connection between the free edge and the outsideof the base portion at said end.

2. A package according to claim 1 wherein the base portion is bentinwardly all around its periphery at said end.

3. A package according to claim 1, wherein said package base portion isrectangular and wherein the stiff material is a plastic-coated cardboardand said end closure is a plastic film.

4. A package according to claim 1, in which a crease line is applied onthe inner side of the stiff cardboard material of the base portionbetween the sides thereof and the pasting flaps, said crease line beingarranged at least substantially to receive a portion of the material ofthe sides of the base portion when the part thereof adjacent said end isbent in to form said frustrum pyramid.

5. A package according to claim 1, wherein the outward extent of thefree edge of the end closure is reduced at the corners of the packagerelative to its outward extent at the sides between said corners.

1. A package having a base portion of a polygonal cross section which isproduced by folding a blank of stiff material such as cardboard or thelike along creased lines such that at least one end of the packagecomprises inwardly directed pasting flaps, a thin foil end closureattached at said end, said pasting flaps being cut at their ends suchthat the ends of the flaps approximately contact each other when thecardboard blank is folded to its form, polygonal in cross section, thesaid end closure of the package at said end comprising a heat-sealablematerial capable of being heat sealed against the cardboard at the saidend of the package and the end closure part including a free edgeextending outside of the edge of the base portion of the package andadapted to be folded down against the outside of the sides of the baseportion and to be attached to the sides thereof, the free edge of thesaid end closure, together with the part of the base portion connectedthereto, at least adjacent to the corners between adjacent sides of thebase portion and at said end, being bent inwardly towards the center ofthe package such that the bent end portions at said end form a frustrumpyramid with the sides at least at said corners, sloping inwardly in thedirection toward the end of the package such that a flattening takesplace of the said free edges of the end closure against the base portionto provide an airtight connection between the free edge and the outsideof the base portion at said end.
 2. A package according to claim 1wherein the base portion is bent inwardly all around its periphery atsaid end.
 3. A package according to claim 1, wherein said package baseportion is rectangular and wherein the stiff material is aplastic-coated cardboard and said end closure is a plastic film.
 4. Apackage according to claim 1, in which a crease line is applied on theinner side of the stiff cardboard material of the base portion betweenthe sides thereof and the pasting flaps, said crease line being arrangedat least substantially to receive a portion of the material of the sidesof the base portion when the part thereof adjacent said end is bent into form said frustrum pyramid.
 5. A package according to claim 1,wherein the outward extent of the free edge of the end closure isreduced at the corners of the package relative to its outward extent atthe sides between said corners.